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			<h1>Python3 <span class="color_h1">列表</span></h1>
<p>序列是 Python 中最基本的数据结构。</p><p>序列中的每个值都有对应的位置值，称之为索引，第一个索引是 0，第二个索引是 1，依此类推。</p>

<p> Python 有 6 个序列的内置类型，但最常见的是列表和元组。</p>

<p>列表都可以进行的操作包括索引，切片，加，乘，检查成员。</p>
<p>此外，Python 已经内置确定序列的长度以及确定最大和最小的元素的方法。</p>

<p>列表是最常用的 Python 数据类型，它可以作为一个方括号内的逗号分隔值出现。</p>
<p>列表的数据项不需要具有相同的类型</p>
<p>创建一个列表，只要把逗号分隔的不同的数据项使用方括号括起来即可。如下所示：</p>
<div class="example">
<div class="example_code">
<div class="hl-main"><span class="hl-identifier">list1</span><span class="hl-code"> = </span><span class="hl-brackets">[</span><span class="hl-quotes">'</span><span class="hl-string">Google</span><span class="hl-quotes">'</span><span class="hl-code">, </span><span class="hl-quotes">'</span><span class="hl-string">Runoob</span><span class="hl-quotes">'</span><span class="hl-code">, </span><span class="hl-number">1997</span><span class="hl-code">, </span><span class="hl-number">2000</span><span class="hl-brackets">]</span><span class="hl-code">
</span><span class="hl-identifier">list2</span><span class="hl-code"> = </span><span class="hl-brackets">[</span><span class="hl-number">1</span><span class="hl-code">, </span><span class="hl-number">2</span><span class="hl-code">, </span><span class="hl-number">3</span><span class="hl-code">, </span><span class="hl-number">4</span><span class="hl-code">, </span><span class="hl-number">5</span><span class="hl-code"> </span><span class="hl-brackets">]</span><span class="hl-code">
</span><span class="hl-identifier">list3</span><span class="hl-code"> = </span><span class="hl-brackets">[</span><span class="hl-quotes">&quot;</span><span class="hl-string">a</span><span class="hl-quotes">&quot;</span><span class="hl-code">, </span><span class="hl-quotes">&quot;</span><span class="hl-string">b</span><span class="hl-quotes">&quot;</span><span class="hl-code">, </span><span class="hl-quotes">&quot;</span><span class="hl-string">c</span><span class="hl-quotes">&quot;</span><span class="hl-code">, </span><span class="hl-quotes">&quot;</span><span class="hl-string">d</span><span class="hl-quotes">&quot;</span><span class="hl-brackets">]</span><span class="hl-code">
</span><span class="hl-identifier">list4</span><span class="hl-code"> = </span><span class="hl-brackets">[</span><span class="hl-quotes">'</span><span class="hl-string">red</span><span class="hl-quotes">'</span><span class="hl-code">, </span><span class="hl-quotes">'</span><span class="hl-string">green</span><span class="hl-quotes">'</span><span class="hl-code">, </span><span class="hl-quotes">'</span><span class="hl-string">blue</span><span class="hl-quotes">'</span><span class="hl-code">, </span><span class="hl-quotes">'</span><span class="hl-string">yellow</span><span class="hl-quotes">'</span><span class="hl-code">, </span><span class="hl-quotes">'</span><span class="hl-string">white</span><span class="hl-quotes">'</span><span class="hl-code">, </span><span class="hl-quotes">'</span><span class="hl-string">black</span><span class="hl-quotes">'</span><span class="hl-brackets">]</span></div>
</div>
</div><hr>
<h2>访问列表中的值</h2>
<p>与字符串的索引一样，列表索引从 <span class="marked">0</span> 开始，第二个索引是 <span class="marked">1</span>，依此类推。</p>
<p>通过索引列表可以进行截取、组合等操作。</p>
<p><img decoding="async" src="https://www.runoob.com/wp-content/uploads/2014/05/positive-indexes-1.png" ></p>
<div class="example"><h2 class="example">实例</h2> <div class="example_code">
<span style="color: #a50">#!/usr/bin/python3</span><br />
<br />
<span style="color: Teal;">list</span> <span style="color: Gray;">=</span> <span style="color: Olive;">&#91;</span><span style="color: #a11;">'red'</span><span style="color: Gray;">,</span> <span style="color: #a11;">'green'</span><span style="color: Gray;">,</span> <span style="color: #a11;">'blue'</span><span style="color: Gray;">,</span> <span style="color: #a11;">'yellow'</span><span style="color: Gray;">,</span> <span style="color: #a11;">'white'</span><span style="color: Gray;">,</span> <span style="color: #a11;">'black'</span><span style="color: Olive;">&#93;</span><br />
<span style="color: Green;font-weight:bold;">print</span><span style="color: Olive;">&#40;</span> <span style="color: Teal;">list</span><span style="color: Olive;">&#91;</span><span style="color: Maroon;">0</span><span style="color: Olive;">&#93;</span> <span style="color: Olive;">&#41;</span><br />
<span style="color: Green;font-weight:bold;">print</span><span style="color: Olive;">&#40;</span> <span style="color: Teal;">list</span><span style="color: Olive;">&#91;</span><span style="color: Maroon;">1</span><span style="color: Olive;">&#93;</span> <span style="color: Olive;">&#41;</span><br />
<span style="color: Green;font-weight:bold;">print</span><span style="color: Olive;">&#40;</span> <span style="color: Teal;">list</span><span style="color: Olive;">&#91;</span><span style="color: Maroon;">2</span><span style="color: Olive;">&#93;</span> <span style="color: Olive;">&#41;</span><br />
</div></div>
<p>以上实例输出结果：</p>
<pre>red
green
blue</pre>
<p>索引也可以从尾部开始，最后一个元素的索引为 <span class="marked">-1</span>，往前一位为 <span class="marked">-2</span>，以此类推。</p>
<p><img decoding="async" src="https://www.runoob.com/wp-content/uploads/2014/05/negative-indexes.png" ></p>
<div class="example"><h2 class="example">实例</h2> <div class="example_code">
<span style="color: #a50">#!/usr/bin/python3</span><br />
<br />
<span style="color: Teal;">list</span> <span style="color: Gray;">=</span> <span style="color: Olive;">&#91;</span><span style="color: #a11;">'red'</span><span style="color: Gray;">,</span> <span style="color: #a11;">'green'</span><span style="color: Gray;">,</span> <span style="color: #a11;">'blue'</span><span style="color: Gray;">,</span> <span style="color: #a11;">'yellow'</span><span style="color: Gray;">,</span> <span style="color: #a11;">'white'</span><span style="color: Gray;">,</span> <span style="color: #a11;">'black'</span><span style="color: Olive;">&#93;</span><br />
<span style="color: Green;font-weight:bold;">print</span><span style="color: Olive;">&#40;</span> <span style="color: Teal;">list</span><span style="color: Olive;">&#91;</span>-<span style="color: Maroon;">1</span><span style="color: Olive;">&#93;</span> <span style="color: Olive;">&#41;</span><br />
<span style="color: Green;font-weight:bold;">print</span><span style="color: Olive;">&#40;</span> <span style="color: Teal;">list</span><span style="color: Olive;">&#91;</span>-<span style="color: Maroon;">2</span><span style="color: Olive;">&#93;</span> <span style="color: Olive;">&#41;</span><br />
<span style="color: Green;font-weight:bold;">print</span><span style="color: Olive;">&#40;</span> <span style="color: Teal;">list</span><span style="color: Olive;">&#91;</span>-<span style="color: Maroon;">3</span><span style="color: Olive;">&#93;</span> <span style="color: Olive;">&#41;</span><br />
</div></div>
<p>以上实例输出结果：</p>
<pre>black
white
yellow</pre>


<p>使用下标索引来访问列表中的值，同样你也可以使用方括号 <span class="marked">[]</span> 的形式截取字符，如下所示：</p>
<p><img decoding="async" src="https://www.runoob.com/wp-content/uploads/2014/05/first-slice.png"></p>
<div class="example"><h2 class="example">实例</h2> <div class="example_code">
<span style="color: #a50">#!/usr/bin/python3</span><br />
<br />
nums <span style="color: Gray;">=</span> <span style="color: Olive;">&#91;</span><span style="color: Maroon;">10</span><span style="color: Gray;">,</span> <span style="color: Maroon;">20</span><span style="color: Gray;">,</span> <span style="color: Maroon;">30</span><span style="color: Gray;">,</span> <span style="color: Maroon;">40</span><span style="color: Gray;">,</span> <span style="color: Maroon;">50</span><span style="color: Gray;">,</span> <span style="color: Maroon;">60</span><span style="color: Gray;">,</span> <span style="color: Maroon;">70</span><span style="color: Gray;">,</span> <span style="color: Maroon;">80</span><span style="color: Gray;">,</span> <span style="color: Maroon;">90</span><span style="color: Olive;">&#93;</span><br />
<span style="color: Green;font-weight:bold;">print</span><span style="color: Olive;">&#40;</span>nums<span style="color: Olive;">&#91;</span><span style="color: Maroon;">0</span>:<span style="color: Maroon;">4</span><span style="color: Olive;">&#93;</span><span style="color: Olive;">&#41;</span><br />
</div></div>
<p>以上实例输出结果：</p>
<pre>
[10, 20, 30, 40]
</pre>
<p>使用负数索引值截取：</p>
<div class="example"> 
<h2 class="example">实例</h2> 
<div class="example_code">
<div class="hl-main"><span class="hl-comment">#!/usr/bin/python3</span><span class="hl-code">
 
</span><span class="hl-identifier">list</span><span class="hl-code"> = </span><span class="hl-brackets">[</span><span class="hl-quotes">'</span><span class="hl-string">Google</span><span class="hl-quotes">'</span><span class="hl-code">, </span><span class="hl-quotes">'</span><span class="hl-string">Runoob</span><span class="hl-quotes">'</span><span class="hl-code">, </span><span class="hl-quotes">&quot;</span><span class="hl-string">Zhihu</span><span class="hl-quotes">&quot;</span><span class="hl-code">, </span><span class="hl-quotes">&quot;</span><span class="hl-string">Taobao</span><span class="hl-quotes">&quot;</span><span class="hl-code">, </span><span class="hl-quotes">&quot;</span><span class="hl-string">Wiki</span><span class="hl-quotes">&quot;</span><span class="hl-brackets">]</span><span class="hl-code">
 
</span><span class="hl-comment"># 读取第二位</span><span class="hl-code">
</span><span class="hl-identifier">print</span><span class="hl-code"> </span><span class="hl-brackets">(</span><span class="hl-quotes">&quot;</span><span class="hl-string">list[1]: </span><span class="hl-quotes">&quot;</span><span class="hl-code">, </span><span class="hl-identifier">list</span><span class="hl-brackets">[</span><span class="hl-number">1</span><span class="hl-brackets">]</span><span class="hl-brackets">)</span><span class="hl-code">
</span><span class="hl-comment"># 从第二位开始（包含）截取到倒数第二位（不包含）</span><span class="hl-code">
</span><span class="hl-identifier">print</span><span class="hl-code"> </span><span class="hl-brackets">(</span><span class="hl-quotes">&quot;</span><span class="hl-string">list[1:-2]: </span><span class="hl-quotes">&quot;</span><span class="hl-code">, </span><span class="hl-identifier">list</span><span class="hl-brackets">[</span><span class="hl-number">1</span><span class="hl-code">:-</span><span class="hl-number">2</span><span class="hl-brackets">]</span><span class="hl-brackets">)</span></div>
</div>

</div>
<p>以上实例输出结果：</p>
<pre>
list[1]:  Runoob
list[1:-2]:  ['Runoob', 'Zhihu']
</pre>
<hr>
<h2>更新列表</h2>
<p>你可以对列表的数据项进行修改或更新，你也可以使用 append() 方法来添加列表项，如下所示：</p>
<div class="example"> 
<h2 class="example">实例(Python 3.0+)</h2> 
<div class="example_code">
<div class="hl-main"><span class="hl-comment">#!/usr/bin/python3</span><span class="hl-code">
 
</span><span class="hl-identifier">list</span><span class="hl-code"> = </span><span class="hl-brackets">[</span><span class="hl-quotes">'</span><span class="hl-string">Google</span><span class="hl-quotes">'</span><span class="hl-code">, </span><span class="hl-quotes">'</span><span class="hl-string">Runoob</span><span class="hl-quotes">'</span><span class="hl-code">, </span><span class="hl-number">1997</span><span class="hl-code">, </span><span class="hl-number">2000</span><span class="hl-brackets">]</span><span class="hl-code">
 
</span><span class="hl-identifier">print</span><span class="hl-code"> </span><span class="hl-brackets">(</span><span class="hl-quotes">&quot;</span><span class="hl-string">第三个元素为 : </span><span class="hl-quotes">&quot;</span><span class="hl-code">, </span><span class="hl-identifier">list</span><span class="hl-brackets">[</span><span class="hl-number">2</span><span class="hl-brackets">]</span><span class="hl-brackets">)</span><span class="hl-code">
</span><span class="hl-identifier">list</span><span class="hl-brackets">[</span><span class="hl-number">2</span><span class="hl-brackets">]</span><span class="hl-code"> = </span><span class="hl-number">2001</span><span class="hl-code">
</span><span class="hl-identifier">print</span><span class="hl-code"> </span><span class="hl-brackets">(</span><span class="hl-quotes">&quot;</span><span class="hl-string">更新后的第三个元素为 : </span><span class="hl-quotes">&quot;</span><span class="hl-code">, </span><span class="hl-identifier">list</span><span class="hl-brackets">[</span><span class="hl-number">2</span><span class="hl-brackets">]</span><span class="hl-brackets">)</span><span class="hl-code">
 
</span><span class="hl-identifier">list1</span><span class="hl-code"> = </span><span class="hl-brackets">[</span><span class="hl-quotes">'</span><span class="hl-string">Google</span><span class="hl-quotes">'</span><span class="hl-code">, </span><span class="hl-quotes">'</span><span class="hl-string">Runoob</span><span class="hl-quotes">'</span><span class="hl-code">, </span><span class="hl-quotes">'</span><span class="hl-string">Taobao</span><span class="hl-quotes">'</span><span class="hl-brackets">]</span><span class="hl-code">
</span><span class="hl-identifier">list1</span><span class="hl-code">.</span><span class="hl-identifier">append</span><span class="hl-brackets">(</span><span class="hl-quotes">'</span><span class="hl-string">Baidu</span><span class="hl-quotes">'</span><span class="hl-brackets">)</span><span class="hl-code">
</span><span class="hl-identifier">print</span><span class="hl-code"> </span><span class="hl-brackets">(</span><span class="hl-quotes">&quot;</span><span class="hl-string">更新后的列表 : </span><span class="hl-quotes">&quot;</span><span class="hl-code">, </span><span class="hl-identifier">list1</span><span class="hl-brackets">)</span></div>
</div>
</div><p><strong>注意：</strong>我们会在接下来的章节讨论 <a href="../python3/python3-att-list-append.html" rel="noopener" target="_blank">append()</a> 方法的使用。</p>
<p>以上实例输出结果：</p>
<pre>
第三个元素为 :  1997
更新后的第三个元素为 :  2001
更新后的列表 :  ['Google', 'Runoob', 'Taobao', 'Baidu']
</pre>
<hr>
<h2>删除列表元素</h2>
<p>可以使用 del 语句来删除列表的的元素，如下实例：</p>
<div class="example"> 
<h2 class="example">实例(Python 3.0+)</h2> 
<div class="example_code">
<div class="hl-main"><span class="hl-comment">#!/usr/bin/python3</span><span class="hl-code">
 
</span><span class="hl-identifier">list</span><span class="hl-code"> = </span><span class="hl-brackets">[</span><span class="hl-quotes">'</span><span class="hl-string">Google</span><span class="hl-quotes">'</span><span class="hl-code">, </span><span class="hl-quotes">'</span><span class="hl-string">Runoob</span><span class="hl-quotes">'</span><span class="hl-code">, </span><span class="hl-number">1997</span><span class="hl-code">, </span><span class="hl-number">2000</span><span class="hl-brackets">]</span><span class="hl-code">
 
</span><span class="hl-identifier">print</span><span class="hl-code"> </span><span class="hl-brackets">(</span><span class="hl-quotes">&quot;</span><span class="hl-string">原始列表 : </span><span class="hl-quotes">&quot;</span><span class="hl-code">, </span><span class="hl-identifier">list</span><span class="hl-brackets">)</span><span class="hl-code">
</span><span class="hl-reserved">del</span><span class="hl-code"> </span><span class="hl-identifier">list</span><span class="hl-brackets">[</span><span class="hl-number">2</span><span class="hl-brackets">]</span><span class="hl-code">
</span><span class="hl-identifier">print</span><span class="hl-code"> </span><span class="hl-brackets">(</span><span class="hl-quotes">&quot;</span><span class="hl-string">删除第三个元素 : </span><span class="hl-quotes">&quot;</span><span class="hl-code">, </span><span class="hl-identifier">list</span><span class="hl-brackets">)</span></div>
</div>
</div><p>以上实例输出结果：</p><pre>
原始列表 :  ['Google', 'Runoob', 1997, 2000]
删除第三个元素 :  ['Google', 'Runoob', 2000]
</pre>
<p><strong>注意：</strong>我们会在接下来的章节讨论 remove() 方法的使用</p>

<hr>
<h2>Python列表脚本操作符</h2>
<p>列表对 + 和  * 的操作符与字符串相似。+ 号用于组合列表，* 号用于重复列表。</p>
<p>如下所示：</p>
<table class="reference">
<tbody><tr>
<th>Python 表达式</th><th>结果 </th><th> 描述</th></tr>
<tr><td>len([1, 2, 3])</td><td>3</td><td>长度</td></tr>
<tr><td>[1, 2, 3] + [4, 5, 6]</td><td>[1, 2, 3, 4, 5, 6]</td><td>组合</td></tr>
<tr><td>['Hi!'] * 4</td><td>['Hi!', 'Hi!', 'Hi!', 'Hi!']</td><td>重复</td></tr>
<tr><td>3 in [1, 2, 3]</td><td>True</td><td>元素是否存在于列表中</td></tr>
<tr><td>for x in [1, 2, 3]: print(x, end=" ")</td><td>1 2 3</td><td>迭代</td></tr>
</tbody></table>

<hr>
<h2>Python列表截取与拼接</h2>
<p>Python的列表截取与字符串操作类型，如下所示：</p>
<div class="example">
<div class="example_code">
<div class="hl-main"><span class="hl-identifier">L</span><span class="hl-code">=</span><span class="hl-brackets">[</span><span class="hl-quotes">'</span><span class="hl-string">Google</span><span class="hl-quotes">'</span><span class="hl-code">, </span><span class="hl-quotes">'</span><span class="hl-string">Runoob</span><span class="hl-quotes">'</span><span class="hl-code">, </span><span class="hl-quotes">'</span><span class="hl-string">Taobao</span><span class="hl-quotes">'</span><span class="hl-brackets">]</span></div>
</div>
</div>
<p>操作：</p>
<table class="reference">
<tbody><tr>
<th style="width:33%">Python 表达式</th><th style="width:33%">结果 </th><th style="width:33%"> 描述</th></tr>
<tr><td>L[2]</td><td>'Taobao'</td><td>读取第三个元素</td></tr>
<tr><td>L[-2]</td><td>'Runoob'</td><td>从右侧开始读取倒数第二个元素: count from the right</td></tr>
<tr><td>L[1:]</td><td>['Runoob', 'Taobao']</td><td>输出从第二个元素开始后的所有元素</td></tr>
</tbody></table>
<div class="example">
<div class="example_code">
<div class="hl-main"><span class="hl-code">&gt;&gt;&gt;</span><span class="hl-identifier">L</span><span class="hl-code">=</span><span class="hl-brackets">[</span><span class="hl-quotes">'</span><span class="hl-string">Google</span><span class="hl-quotes">'</span><span class="hl-code">, </span><span class="hl-quotes">'</span><span class="hl-string">Runoob</span><span class="hl-quotes">'</span><span class="hl-code">, </span><span class="hl-quotes">'</span><span class="hl-string">Taobao</span><span class="hl-quotes">'</span><span class="hl-brackets">]</span><span class="hl-code">
&gt;&gt;&gt; </span><span class="hl-identifier">L</span><span class="hl-brackets">[</span><span class="hl-number">2</span><span class="hl-brackets">]</span><span class="hl-code">
</span><span class="hl-quotes">'</span><span class="hl-string">Taobao</span><span class="hl-quotes">'</span><span class="hl-code">
&gt;&gt;&gt; </span><span class="hl-identifier">L</span><span class="hl-brackets">[</span><span class="hl-code">-</span><span class="hl-number">2</span><span class="hl-brackets">]</span><span class="hl-code">
</span><span class="hl-quotes">'</span><span class="hl-string">Runoob</span><span class="hl-quotes">'</span><span class="hl-code">
&gt;&gt;&gt; </span><span class="hl-identifier">L</span><span class="hl-brackets">[</span><span class="hl-number">1</span><span class="hl-code">:</span><span class="hl-brackets">]</span><span class="hl-code">
</span><span class="hl-brackets">[</span><span class="hl-quotes">'</span><span class="hl-string">Runoob</span><span class="hl-quotes">'</span><span class="hl-code">, </span><span class="hl-quotes">'</span><span class="hl-string">Taobao</span><span class="hl-quotes">'</span><span class="hl-brackets">]</span><span class="hl-code">
&gt;&gt;&gt;</span></div>
</div>
</div>
<p>列表还支持拼接操作：</p>
<div class="example">
<div class="example_code">
<div class="hl-main"><span class="hl-code">&gt;&gt;&gt;</span><span class="hl-identifier">squares</span><span class="hl-code"> = </span><span class="hl-brackets">[</span><span class="hl-number">1</span><span class="hl-code">, </span><span class="hl-number">4</span><span class="hl-code">, </span><span class="hl-number">9</span><span class="hl-code">, </span><span class="hl-number">16</span><span class="hl-code">, </span><span class="hl-number">25</span><span class="hl-brackets">]</span><span class="hl-code">
&gt;&gt;&gt; </span><span class="hl-identifier">squares</span><span class="hl-code"> += </span><span class="hl-brackets">[</span><span class="hl-number">36</span><span class="hl-code">, </span><span class="hl-number">49</span><span class="hl-code">, </span><span class="hl-number">64</span><span class="hl-code">, </span><span class="hl-number">81</span><span class="hl-code">, </span><span class="hl-number">100</span><span class="hl-brackets">]</span><span class="hl-code">
&gt;&gt;&gt; </span><span class="hl-identifier">squares</span><span class="hl-code">
</span><span class="hl-brackets">[</span><span class="hl-number">1</span><span class="hl-code">, </span><span class="hl-number">4</span><span class="hl-code">, </span><span class="hl-number">9</span><span class="hl-code">, </span><span class="hl-number">16</span><span class="hl-code">, </span><span class="hl-number">25</span><span class="hl-code">, </span><span class="hl-number">36</span><span class="hl-code">, </span><span class="hl-number">49</span><span class="hl-code">, </span><span class="hl-number">64</span><span class="hl-code">, </span><span class="hl-number">81</span><span class="hl-code">, </span><span class="hl-number">100</span><span class="hl-brackets">]</span><span class="hl-code">
&gt;&gt;&gt;</span></div>
</div>
</div>
<hr>
<h2>嵌套列表</h2>
<p>使用嵌套列表即在列表里创建其它列表，例如：</p>
<div class="example">
<div class="example_code">
<div class="hl-main"><span class="hl-code">&gt;&gt;&gt;</span><span class="hl-identifier">a</span><span class="hl-code"> = </span><span class="hl-brackets">[</span><span class="hl-quotes">'</span><span class="hl-string">a</span><span class="hl-quotes">'</span><span class="hl-code">, </span><span class="hl-quotes">'</span><span class="hl-string">b</span><span class="hl-quotes">'</span><span class="hl-code">, </span><span class="hl-quotes">'</span><span class="hl-string">c</span><span class="hl-quotes">'</span><span class="hl-brackets">]</span><span class="hl-code">
&gt;&gt;&gt; </span><span class="hl-identifier">n</span><span class="hl-code"> = </span><span class="hl-brackets">[</span><span class="hl-number">1</span><span class="hl-code">, </span><span class="hl-number">2</span><span class="hl-code">, </span><span class="hl-number">3</span><span class="hl-brackets">]</span><span class="hl-code">
&gt;&gt;&gt; </span><span class="hl-identifier">x</span><span class="hl-code"> = </span><span class="hl-brackets">[</span><span class="hl-identifier">a</span><span class="hl-code">, </span><span class="hl-identifier">n</span><span class="hl-brackets">]</span><span class="hl-code">
&gt;&gt;&gt; </span><span class="hl-identifier">x</span><span class="hl-code">
</span><span class="hl-brackets">[</span><span class="hl-brackets">[</span><span class="hl-quotes">'</span><span class="hl-string">a</span><span class="hl-quotes">'</span><span class="hl-code">, </span><span class="hl-quotes">'</span><span class="hl-string">b</span><span class="hl-quotes">'</span><span class="hl-code">, </span><span class="hl-quotes">'</span><span class="hl-string">c</span><span class="hl-quotes">'</span><span class="hl-brackets">]</span><span class="hl-code">, </span><span class="hl-brackets">[</span><span class="hl-number">1</span><span class="hl-code">, </span><span class="hl-number">2</span><span class="hl-code">, </span><span class="hl-number">3</span><span class="hl-brackets">]</span><span class="hl-brackets">]</span><span class="hl-code">
&gt;&gt;&gt; </span><span class="hl-identifier">x</span><span class="hl-brackets">[</span><span class="hl-number">0</span><span class="hl-brackets">]</span><span class="hl-code">
</span><span class="hl-brackets">[</span><span class="hl-quotes">'</span><span class="hl-string">a</span><span class="hl-quotes">'</span><span class="hl-code">, </span><span class="hl-quotes">'</span><span class="hl-string">b</span><span class="hl-quotes">'</span><span class="hl-code">, </span><span class="hl-quotes">'</span><span class="hl-string">c</span><span class="hl-quotes">'</span><span class="hl-brackets">]</span><span class="hl-code">
&gt;&gt;&gt; </span><span class="hl-identifier">x</span><span class="hl-brackets">[</span><span class="hl-number">0</span><span class="hl-brackets">]</span><span class="hl-brackets">[</span><span class="hl-number">1</span><span class="hl-brackets">]</span><span class="hl-code">
</span><span class="hl-quotes">'</span><span class="hl-string">b</span><span class="hl-quotes">'</span></div>
</div>
</div>

<hr>
<h2>列表比较</h2><p>
列表比较需要引入 <span class="marked">operator</span> 模块的 <span class="marked">eq</span> 方法（详见：<a href="../python3/python-operator.html" rel="noopener" target="_blank">Python operator 模块</a>）：</p>
<div class="example"><h2 class="example">实例</h2> <div class="example_code">
<span style="color: #a50"># 导入 operator 模块</span><br />
<span style="color: Green;font-weight:bold;">import</span> <span style="color: #05a;">operator</span><br />
<br />
a <span style="color: Gray;">=</span> <span style="color: Olive;">&#91;</span><span style="color: Maroon;">1</span><span style="color: Gray;">,</span> <span style="color: Maroon;">2</span><span style="color: Olive;">&#93;</span><br />
b <span style="color: Gray;">=</span> <span style="color: Olive;">&#91;</span><span style="color: Maroon;">2</span><span style="color: Gray;">,</span> <span style="color: Maroon;">3</span><span style="color: Olive;">&#93;</span><br />
c <span style="color: Gray;">=</span> <span style="color: Olive;">&#91;</span><span style="color: Maroon;">2</span><span style="color: Gray;">,</span> <span style="color: Maroon;">3</span><span style="color: Olive;">&#93;</span><br />
<span style="color: Green;font-weight:bold;">print</span><span style="color: Olive;">&#40;</span><span style="color: #a11;">&quot;operator.eq(a,b): &quot;</span><span style="color: Gray;">,</span> <span style="color: #05a;">operator</span>.<span style="color: #05a;">eq</span><span style="color: Olive;">&#40;</span>a<span style="color: Gray;">,</span>b<span style="color: Olive;">&#41;</span><span style="color: Olive;">&#41;</span><br />
<span style="color: Green;font-weight:bold;">print</span><span style="color: Olive;">&#40;</span><span style="color: #a11;">&quot;operator.eq(c,b): &quot;</span><span style="color: Gray;">,</span> <span style="color: #05a;">operator</span>.<span style="color: #05a;">eq</span><span style="color: Olive;">&#40;</span>c<span style="color: Gray;">,</span>b<span style="color: Olive;">&#41;</span><span style="color: Olive;">&#41;</span><br />
</div></div>
<p>以上代码输出结果为：</p>

<pre>operator.eq(a,b):  False
operator.eq(c,b):  True</pre>
<hr>
<h2>Python列表函数&方法</h2>
<p>Python包含以下函数:</p>
<table class="reference">
<tbody><tr>
<th style="width:5%">序号</th><th style="width:95%">函数</th></tr>

<tr><td>1</td><td><a href="python3-att-list-len.html">len(list)</a><br>列表元素个数</td></tr>
<tr><td>2</td><td><a href="python3-att-list-max.html">max(list)</a><br>返回列表元素最大值</td></tr>
<tr><td>3</td><td><a href="python3-att-list-min.html">min(list)</a><br>返回列表元素最小值</td></tr>
<tr><td>4</td><td><a href="python3-att-list-list.html">list(seq)</a><br>将元组转换为列表</td></tr>
</tbody></table>
<p>Python包含以下方法:</p>
<table class="reference">
<tbody><tr>
<th style="width:5%">序号</th><th style="width:95%">方法</th></tr>
<tr><td>1</td><td><a href="python3-att-list-append.html">list.append(obj)</a><br>在列表末尾添加新的对象</td></tr>
<tr><td>2</td><td><a href="python3-att-list-count.html">list.count(obj)</a><br>统计某个元素在列表中出现的次数</td></tr>
<tr><td>3</td><td><a href="python3-att-list-extend.html">list.extend(seq)</a><br>在列表末尾一次性追加另一个序列中的多个值（用新列表扩展原来的列表）</td></tr>
<tr><td>4</td><td><a href="python3-att-list-index.html">list.index(obj)</a><br>从列表中找出某个值第一个匹配项的索引位置</td></tr>
<tr><td>5</td><td><a href="python3-att-list-insert.html">list.insert(index, obj)</a><br>将对象插入列表</td></tr>
<tr><td>6</td><td><a href="python3-att-list-pop.html">list.pop([index=-1])</a><br>移除列表中的一个元素（默认最后一个元素），并且返回该元素的值</td></tr>
<tr><td>7</td><td><a href="python3-att-list-remove.html">list.remove(obj)</a><br>移除列表中某个值的第一个匹配项</td></tr>
<tr><td>8</td><td><a href="python3-att-list-reverse.html">list.reverse()</a><br>反向列表中元素</td></tr>
<tr><td>9</td><td><a href="python3-att-list-sort.html">	list.sort( key=None, reverse=False)</a><br>对原列表进行排序</td></tr>
<tr><td>10</td><td><a href="python3-att-list-clear.html">list.clear()</a><br>清空列表</td></tr>
<tr><td>11</td><td><a href="python3-att-list-copy.html">list.copy()</a><br>复制列表</td></tr>
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		<li class="comment byuser comment-author-tianqixin bypostauthor even thread-even depth-1" id="comment-1038"><span class="comt-f">#0</span><div class="comt-avatar wrapper"><i style="font-size:36px;" class="fa fa-user-circle" aria-hidden="true"></i><div class="tooltip"><p><i class="fa fa-user" aria-hidden="true"></i>&nbsp;&nbsp;&nbsp;tianqixin</p><p><i class="fa fa-envelope" aria-hidden="true"></i>&nbsp;&nbsp;429***967@qq.com</p><p><i class="fa fa-external-link" aria-hidden="true"></i> <a rel="nofollow" target="_blank" href="http://www.runoob.com">&nbsp;&nbsp;参考地址</a></p></div><div id="runoobvote-id-1038" data-commid = "1038" class="upvotejs"><a class="upvote"></a> <span class="count">184</span></div></div><div class="comt-main" id="div-comment-1038"><p>python 创建二维列表，将需要的参数写入 cols 和 rows 即可</p>

<pre>list_2d = [[0 for col in range(cols)] for row in range(rows)]
</pre>

<p><strong>实例：</strong></p>

<pre>
&gt;&gt;&gt; list_2d = [ [0 for i in range(5)] for i in range(5)]
&gt;&gt;&gt; list_2d[0].append(3)
&gt;&gt;&gt; list_2d[0].append(5)
&gt;&gt;&gt; list_2d[2].append(7)
&gt;&gt;&gt; list_2d
[[0, 0, 0, 0, 0, 3, 5], [0, 0, 0, 0, 0], [0, 0, 0, 0, 0, 7], [0, 0, 0, 0, 0], [0, 0, 0, 0, 0]]
</pre><div class="comt-meta wrapper"><span class="comt-author"><a target="_blank" href="javascript:;">tianqixin</a><div class="tooltip tooltip1"><p><i class="fa fa-user" aria-hidden="true"></i>&nbsp;&nbsp;&nbsp;tianqixin</p><p><i class="fa fa-envelope" aria-hidden="true"></i>&nbsp;&nbsp;429***967@qq.com</p><p><i class="fa fa-external-link" aria-hidden="true"></i> <a rel="nofollow" target="_blank" href="http://www.runoob.com">&nbsp;&nbsp;参考地址</a></p></div></span>6年前 (2017-02-25)</div></div></li><!-- #comment-## -->
<li class="comment odd alt thread-odd thread-alt depth-1" id="comment-13135"><span class="comt-f">#0</span><div class="comt-avatar wrapper"><i style="font-size:36px;" class="fa fa-user-circle" aria-hidden="true"></i><div class="tooltip"><p><i class="fa fa-user" aria-hidden="true"></i>&nbsp;&nbsp;&nbsp;打杂的</p><p><i class="fa fa-envelope" aria-hidden="true"></i>&nbsp;&nbsp;854***070@qq.com</p></div><div id="runoobvote-id-13135" data-commid = "13135" class="upvotejs"><a class="upvote"></a> <span class="count">274</span></div></div><div class="comt-main" id="div-comment-13135"><p>分享一个例子，刚学，错了别喷:
</p><pre>
l = [i for i in range(0,15)]
print(l[::2])</pre><p>
我们可以看到l后面跟了两个冒号，还有个 2 ，效果：</p>
<pre>
&gt;&gt;&gt; l = [i for i in range(0,15)]
&gt;&gt;&gt; print(l[::2])
[0, 2, 4, 6, 8, 10, 12, 14]</pre><p>
我理解为:</p>
<pre>
l[start:end:span]</pre><p>遍历 [start,end)，间隔为 span，当 span&gt;0 时顺序遍历, 当 span&lt;0 时，逆着遍历。</p><p>
start 不输入则默认为 0，end 不输入默认为长度。</p><div class="comt-meta wrapper"><span class="comt-author"><a target="_blank" href="javascript:;">打杂的</a><div class="tooltip tooltip1"><p><i class="fa fa-user" aria-hidden="true"></i>&nbsp;&nbsp;&nbsp;打杂的</p><p><i class="fa fa-envelope" aria-hidden="true"></i>&nbsp;&nbsp;854***070@qq.com</p></div></span>6年前 (2017-06-19)</div></div></li><!-- #comment-## -->
<li class="comment even thread-even depth-1" id="comment-13883"><span class="comt-f">#0</span><div class="comt-avatar wrapper"><i style="font-size:36px;" class="fa fa-user-circle" aria-hidden="true"></i><div class="tooltip"><p><i class="fa fa-user" aria-hidden="true"></i>&nbsp;&nbsp;&nbsp;c@sm</p><p><i class="fa fa-envelope" aria-hidden="true"></i>&nbsp;&nbsp;149***624@qq.com</p></div><div id="runoobvote-id-13883" data-commid = "13883" class="upvotejs"><a class="upvote"></a> <span class="count">173</span></div></div><div class="comt-main" id="div-comment-13883"><p><strong>列表的复制</strong></p>
<pre>
&gt;&gt;&gt; a = [1, 2, 3]
&gt;&gt;&gt; b = a
&gt;&gt;&gt; c = []
&gt;&gt;&gt; c = a
&gt;&gt;&gt; d = a[:]
&gt;&gt;&gt; a, b, c, d
([1, 2, 3], [1, 2, 3], [1, 2, 3], [1, 2, 3])
&gt;&gt;&gt; b[0] = 'b'
&gt;&gt;&gt; a, b, c, d
(['b', 2, 3], ['b', 2, 3], ['b', 2, 3], [1, 2, 3])
&gt;&gt;&gt; id(a), id(b), id(c), id(d)
(140180778120200, 140180778120200, 140180778120200, 140180778122696)
&gt;&gt;&gt; c[0] = 'c'
&gt;&gt;&gt; a, b, c, d
(['c', 2, 3], ['c', 2, 3], ['c', 2, 3], [1, 2, 3])
&gt;&gt;&gt; id(a), id(b), id(c), id(d)
(140180778120200, 140180778120200, 140180778120200, 140180778122696)
&gt;&gt;&gt; d[0] = 'd'
&gt;&gt;&gt; a, b, c, d
(['c', 2, 3], ['c', 2, 3], ['c', 2, 3], ['d', 2, 3])
&gt;&gt;&gt; id(a), id(b), id(c), id(d)
(140180778120200, 140180778120200, 140180778120200, 140180778122696)
</pre>
<p>可以看到a b c 三个是同一id值，当改变当中任一列表元素的值后，三者会同步改变。</p>
<p>但d的元素值不会变，改变d的元素值其它三个变量内的元素值也不会变。</p>
<p>从a b c d 的id值来看，a b c 地址全一样，唯有d分配了新地址。</p>
<p>所以一般情况下想复制得到一个新列表并改变新列表内元素而不影响原列表，可以采用d的赋值方式。</p>
<p>这只是针对这种比较单一的普通列表。</p>
<div class="comt-meta wrapper"><span class="comt-author"><a target="_blank" href="javascript:;">c@sm</a><div class="tooltip tooltip1"><p><i class="fa fa-user" aria-hidden="true"></i>&nbsp;&nbsp;&nbsp;c@sm</p><p><i class="fa fa-envelope" aria-hidden="true"></i>&nbsp;&nbsp;149***624@qq.com</p></div></span>6年前 (2017-07-10)</div></div></li><!-- #comment-## -->
<li class="comment odd alt thread-odd thread-alt depth-1" id="comment-18081"><span class="comt-f">#0</span><div class="comt-avatar wrapper"><i style="font-size:36px;" class="fa fa-user-circle" aria-hidden="true"></i><div class="tooltip"><p><i class="fa fa-user" aria-hidden="true"></i>&nbsp;&nbsp;&nbsp;Lmac</p><p><i class="fa fa-envelope" aria-hidden="true"></i>&nbsp;&nbsp;lma***03@163.com</p></div><div id="runoobvote-id-18081" data-commid = "18081" class="upvotejs"><a class="upvote"></a> <span class="count">68</span></div></div><div class="comt-main" id="div-comment-18081"><p><span class="marked">@sm</span> 同学提到的列表的复制问题，其实可以用copy模块里 copy()函数解决，实例如下：</p>

<pre>import copy

a = [1,2,3,4]
b = a
d = copy.copy(a)
b[0] = 'b'
print(a,b,d)
print(id(a),id(b),id(d))</pre><div class="comt-meta wrapper"><span class="comt-author"><a target="_blank" href="javascript:;">Lmac</a><div class="tooltip tooltip1"><p><i class="fa fa-user" aria-hidden="true"></i>&nbsp;&nbsp;&nbsp;Lmac</p><p><i class="fa fa-envelope" aria-hidden="true"></i>&nbsp;&nbsp;lma***03@163.com</p></div></span>6年前 (2017-09-25)</div></div></li><!-- #comment-## -->
<li class="comment even thread-even depth-1" id="comment-20001"><span class="comt-f">#0</span><div class="comt-avatar wrapper"><i style="font-size:36px;" class="fa fa-user-circle" aria-hidden="true"></i><div class="tooltip"><p><i class="fa fa-user" aria-hidden="true"></i>&nbsp;&nbsp;&nbsp;david</p><p><i class="fa fa-envelope" aria-hidden="true"></i>&nbsp;&nbsp;185***88@qq.com</p></div><div id="runoobvote-id-20001" data-commid = "20001" class="upvotejs"><a class="upvote"></a> <span class="count">85</span></div></div><div class="comt-main" id="div-comment-20001"><p>楼上两位同学说的都对,还有一个就是用list自带的copy()方法,把重新开辟内存空间存储新列表。</p>


<pre>original_list=[0,1,2,3,4,5,6,7,8]
copy_list=original_list.copy()
copy_list=copy_list+['a','b','c']
print("original_list:",original_list)
print("copy_list modify:",copy_list)</pre>


<p>运行结果</p>


<pre>original_list: [0, 1, 2, 3, 4, 5, 6, 7, 8]
copy_list modify: [0, 1, 2, 3, 4, 5, 6, 7, 8, 'a', 'b', 'c']</pre><div class="comt-meta wrapper"><span class="comt-author"><a target="_blank" href="javascript:;">david</a><div class="tooltip tooltip1"><p><i class="fa fa-user" aria-hidden="true"></i>&nbsp;&nbsp;&nbsp;david</p><p><i class="fa fa-envelope" aria-hidden="true"></i>&nbsp;&nbsp;185***88@qq.com</p></div></span>6年前 (2017-11-08)</div></div></li><!-- #comment-## -->
<li class="comment odd alt thread-odd thread-alt depth-1" id="comment-23519"><span class="comt-f">#0</span><div class="comt-avatar wrapper"><i style="font-size:36px;" class="fa fa-user-circle" aria-hidden="true"></i><div class="tooltip"><p><i class="fa fa-user" aria-hidden="true"></i>&nbsp;&nbsp;&nbsp;182yzh_</p><p><i class="fa fa-envelope" aria-hidden="true"></i>&nbsp;&nbsp;182***6895@qq.com</p></div><div id="runoobvote-id-23519" data-commid = "23519" class="upvotejs"><a class="upvote"></a> <span class="count">72</span></div></div><div class="comt-main" id="div-comment-23519"><p>空列表可以简单地通过两个中括号进行表示([])- 一里面什么东西都没有，但是，如果想创建一个占用十个元素空间，却不包括任何有用内容的列表，又该怎么办呢?首先可以类似于下面的方法，用某一个具体的值代替。</p>

<pre>&gt;&gt;&gt; list_empty = [0]*10
&gt;&gt;&gt; list_empty
[0, 0, 0, 0, 0, 0, 0, 0, 0, 0]</pre>

<p>这样就生成了一一个包括10个0的列表。然而，有时候可能会需要一个值来代表空一意味着没有在里面放置任何元素。这个时候就需要使用None。None 是一个Python的内建值，它的确切含意是"这里什么也没有"。因此，如果想初始化个长度为10的列表，可以按照下面的例子来实现:</p>

<pre>&gt;&gt;&gt; list_empty = [None]*10
&gt;&gt;&gt; list_empty
[None, None, None, None, None, None, None, None, None, None]</pre>

<p>这样就可以再去对list的各个元素进行初始化了</p>

<div class="comt-meta wrapper"><span class="comt-author"><a target="_blank" href="javascript:;">182yzh_</a><div class="tooltip tooltip1"><p><i class="fa fa-user" aria-hidden="true"></i>&nbsp;&nbsp;&nbsp;182yzh_</p><p><i class="fa fa-envelope" aria-hidden="true"></i>&nbsp;&nbsp;182***6895@qq.com</p></div></span>5年前 (2018-01-25)</div></div></li><!-- #comment-## -->
<li class="comment even thread-even depth-1" id="comment-27928"><span class="comt-f">#0</span><div class="comt-avatar wrapper"><i style="font-size:36px;" class="fa fa-user-circle" aria-hidden="true"></i><div class="tooltip"><p><i class="fa fa-user" aria-hidden="true"></i>&nbsp;&nbsp;&nbsp;malan</p><p><i class="fa fa-envelope" aria-hidden="true"></i>&nbsp;&nbsp;may***im.ac.cn</p></div><div id="runoobvote-id-27928" data-commid = "27928" class="upvotejs"><a class="upvote"></a> <span class="count">59</span></div></div><div class="comt-main" id="div-comment-27928"><p>有时在取 list 中元素时可能会遇到以下情形：</p>
<pre>&gt;&gt;&gt; a=[]
&gt;&gt;&gt; a[0]
Traceback (most recent call last):
  File "&lt;stdin&gt;", line 1, in &lt;module&gt;
IndexError: list index out of range</pre>
<p>这种情况发生是因为只定义了一个空列表，没有进行任何的赋值，所以列表里什么也没有，而后面的报错也明确表示了索引超出范围，即写上的0其实是第一位值的位置，而此时是空列表没有赋值，故而报错。</p>
<p>而如果我们使用以下语句则不会报错：</p>
<pre>&gt;&gt;&gt; a[0:]
[]</pre>
<p>这个不是什么小技巧，这是不一样的语句意义，这句话其实是把这个列表 a 里的所有值都输出，其效果和下面表达的最终结果是一致的。</p>

<pre>&gt;&gt;&gt; a[:]
[]</pre>

<p>而这个语句并不能避免上面报错中超出索引范围的错误，这个根本就是两种不同的意义的语句。a[0:] 和 a[:] 在脚本输出时相当于 print(a) 的意思。这不是解决错误的方式，不能将它当成 trick 来用。</p><div class="comt-meta wrapper"><span class="comt-author"><a target="_blank" href="javascript:;">malan</a><div class="tooltip tooltip1"><p><i class="fa fa-user" aria-hidden="true"></i>&nbsp;&nbsp;&nbsp;malan</p><p><i class="fa fa-envelope" aria-hidden="true"></i>&nbsp;&nbsp;may***im.ac.cn</p></div></span>5年前 (2018-05-30)</div></div></li><!-- #comment-## -->
<li class="comment odd alt thread-odd thread-alt depth-1" id="comment-34376"><span class="comt-f">#0</span><div class="comt-avatar wrapper"><i style="font-size:36px;" class="fa fa-user-circle" aria-hidden="true"></i><div class="tooltip"><p><i class="fa fa-user" aria-hidden="true"></i>&nbsp;&nbsp;&nbsp;samson</p><p><i class="fa fa-envelope" aria-hidden="true"></i>&nbsp;&nbsp;492***982@qq.com</p><p><i class="fa fa-external-link" aria-hidden="true"></i> <a rel="nofollow" target="_blank" href="https://www.cnblogs.com/yupeng/p/3428556.html">&nbsp;&nbsp;参考地址</a></p></div><div id="runoobvote-id-34376" data-commid = "34376" class="upvotejs"><a class="upvote"></a> <span class="count">222</span></div></div><div class="comt-main" id="div-comment-34376"><p>感觉少了列表推导式的讲解 (这个功能很方便的)</p>

<p data-title="Python 列表推导式">1、列表推导式书写形式：　　</p>

<pre>[表达式 for 变量 in 列表]
或者
[表达式 for 变量 in 列表 if 条件]</pre>

<p>2、举例说明：</p>

<pre>#!/usr/bin/python
# -*- coding: utf-8 -*-

li = [1,2,3,4,5,6,7,8,9]
print ([x**2 for x in li])

print ([x**2 for x in li if x&gt;5])

print (dict([(x,x*10) for x in li]))


print ([ (x, y) for x in range(10) if x % 2 if x &gt; 3 for y in range(10) if y &gt; 7 if y != 8 ])

vec=[2,4,6]
vec2=[4,3,-9]
sq = [vec[i]+vec2[i] for i in range(len(vec))]
print (sq)

print ([x*y for x in [1,2,3] for y in  [1,2,3]])

testList = [1,2,3,4]
def mul2(x):
    return x*2
print ([mul2(i) for i in testList])</pre>


<p>结果：</p>

<pre>[1, 4, 9, 16, 25, 36, 49, 64, 81]
[36, 49, 64, 81]
{1: 10, 2: 20, 3: 30, 4: 40, 5: 50, 6: 60, 7: 70, 8: 80, 9: 90}
[(5, 9), (7, 9), (9, 9)]
[6, 7, -3]
[1, 2, 3, 2, 4, 6, 3, 6, 9]
[2, 4, 6, 8]</pre>

<p>3、总结：</p>

<p>我觉得就是通过 for 语句处理表达式里面的变量，如果还要加条件，就加 if 条件就可以了。</p><div class="comt-meta wrapper"><span class="comt-author"><a target="_blank" href="../note/34376">samson</a><div class="tooltip tooltip1"><p><i class="fa fa-user" aria-hidden="true"></i>&nbsp;&nbsp;&nbsp;samson</p><p><i class="fa fa-envelope" aria-hidden="true"></i>&nbsp;&nbsp;492***982@qq.com</p><p><i class="fa fa-external-link" aria-hidden="true"></i> <a rel="nofollow" target="_blank" href="https://www.cnblogs.com/yupeng/p/3428556.html">&nbsp;&nbsp;参考地址</a></p></div></span>5年前 (2018-08-24)</div></div></li><!-- #comment-## -->
<li class="comment even thread-even depth-1" id="comment-35398"><span class="comt-f">#0</span><div class="comt-avatar wrapper"><i style="font-size:36px;" class="fa fa-user-circle" aria-hidden="true"></i><div class="tooltip"><p><i class="fa fa-user" aria-hidden="true"></i>&nbsp;&nbsp;&nbsp;GaiFan</p><p><i class="fa fa-envelope" aria-hidden="true"></i>&nbsp;&nbsp;343***128@qq.com</p></div><div id="runoobvote-id-35398" data-commid = "35398" class="upvotejs"><a class="upvote"></a> <span class="count">64</span></div></div><div class="comt-main" id="div-comment-35398"><p>在此教程中未提到列表的切片，在这里简单的说明一下。</p>

<p><strong>格式：</strong> <span class="marked">【start:end:step】</span></p>
<ul><li>
start:起始索引，从0开始，-1表示结束
</li><li>
end：结束索引
</li><li>
step：步长，end-start，步长为正时，从左向右取值。步长为负时，反向取值
</li></ul>
<p>举例说明:</p>

<pre>&gt;&gt;&gt; a=[1,2,3,4]
&gt;&gt;&gt; b='abcdef'
&gt;&gt;&gt; print(a[1:2])
[2]
&gt;&gt;&gt; print(b[2:])
cdef
&gt;&gt;&gt; print(a[::-1])
[4, 3, 2, 1]
&gt;&gt;&gt; print(b[::-1])
fedcba</pre>

<p>如果不是同样追求语法细节的“老鸟”，这段代码的作用恐怕不能第一眼看出来，实际上为了更好的体现 pythonic 的代码是充分利用 python 库里的 reversed() 函数。</p>

<pre>&gt;&gt;&gt; print(list(reversed(a)))
[4, 3, 2, 1]
&gt;&gt;&gt; print(list(reversed(b)))
['f', 'e', 'd', 'c', 'b', 'a']</pre><div class="comt-meta wrapper"><span class="comt-author"><a target="_blank" href="javascript:;">GaiFan</a><div class="tooltip tooltip1"><p><i class="fa fa-user" aria-hidden="true"></i>&nbsp;&nbsp;&nbsp;GaiFan</p><p><i class="fa fa-envelope" aria-hidden="true"></i>&nbsp;&nbsp;343***128@qq.com</p></div></span>5年前 (2018-09-26)</div></div></li><!-- #comment-## -->
<li class="comment odd alt thread-odd thread-alt depth-1" id="comment-36100"><span class="comt-f">#0</span><div class="comt-avatar wrapper"><i style="font-size:36px;" class="fa fa-user-circle" aria-hidden="true"></i><div class="tooltip"><p><i class="fa fa-user" aria-hidden="true"></i>&nbsp;&nbsp;&nbsp;nicergj</p><p><i class="fa fa-envelope" aria-hidden="true"></i>&nbsp;&nbsp;nic***j@163.com</p></div><div id="runoobvote-id-36100" data-commid = "36100" class="upvotejs"><a class="upvote"></a> <span class="count">39</span></div></div><div class="comt-main" id="div-comment-36100"><p><strong>1 通过列表切片方式复制列表：</strong></p>

<p>1.1 列表复制</p>



<pre>my_foods = ['pizza', 'falafel', 'carrot cake']
friend_foods = my_foods[:]
print("My favorite foods are:")
print(my_foods)
print("\nMy friend's favorite foods are:")
print(friend_foods)</pre>

<p>输出：</p>

<pre>My favorite foods are:
['pizza', 'falafel', 'carrot cake'] 
My friend's favorite foods are: 
['pizza', 'falafel', 'carrot cake']</pre>

<p>1.2 验证确实实现了两个列表</p>



<pre>my_foods.append('cannoli')
friend_foods.append('ice cream')
print("My favorite foods are:")
print(my_foods)
print("\nMy friend's favorite foods are:")
print(friend_foods)</pre>

<p>输出：</p>

<pre>My favorite foods are: 
 ['pizza', 'falafel', 'carrot cake', 'cannoli'] 
My friend's favorite foods are: 
 ['pizza', 'falafel', 'carrot cake', 'ice cream']</pre>

<p>可以看出通过切片方式复制列表，结果是生成了两个列表。</p>

<p><strong>2 通过简单赋值方式复制列表：</strong></p>



<pre>my_foods = ['pizza', 'falafel', 'carrot cake']
friend_foods = my_foods
my_foods.append('cannoli')
friend_foods.append('ice cream')
print("My favorite foods are:") 
print(my_foods) 
print("\nMy friend's favorite foods are:") 
print(friend_foods)</pre>

<p>输出：</p>

<pre>My favorite foods are: 
['pizza', 'falafel', 'carrot cake', 'cannoli', 'ice cream'] 
My friend's favorite foods are: 
['pizza', 'falafel', 'carrot cake', 'cannoli', 'ice cream']</pre>

<p>可以看出两个列表是相同的，这并非我们想要的结果。</p><div class="comt-meta wrapper"><span class="comt-author"><a target="_blank" href="javascript:;">nicergj</a><div class="tooltip tooltip1"><p><i class="fa fa-user" aria-hidden="true"></i>&nbsp;&nbsp;&nbsp;nicergj</p><p><i class="fa fa-envelope" aria-hidden="true"></i>&nbsp;&nbsp;nic***j@163.com</p></div></span>5年前 (2018-10-21)</div></div></li><!-- #comment-## -->
<li class="comment byuser comment-author-yota_togashi even thread-even depth-1" id="comment-38080"><span class="comt-f">#0</span><div class="comt-avatar wrapper"><i style="font-size:36px;" class="fa fa-user-circle" aria-hidden="true"></i><div class="tooltip"><p><i class="fa fa-user" aria-hidden="true"></i>&nbsp;&nbsp;&nbsp;Yota_Togashi</p><p><i class="fa fa-envelope" aria-hidden="true"></i>&nbsp;&nbsp;116***47@qq.com</p></div><div id="runoobvote-id-38080" data-commid = "38080" class="upvotejs"><a class="upvote"></a> <span class="count">45</span></div></div><div class="comt-main" id="div-comment-38080"><p>这个例子说明了 Python 列表是链式存储结构，并非顺序存储。</p>
<pre>a=[1,2,3,4]
for i in range(len(a)):
    print(id(a[i]))
a[1]=100
print("----------")
for i in range(len(a)):
    print(id(a[i]))</pre>
<p>输出结果：</p>


<pre>4471499232
4471499264
4471499296
4471499328
----------
4471499232
4471502400
4471499296
4471499328</pre><div class="comt-meta wrapper"><span class="comt-author"><a target="_blank" href="javascript:;">Yota_Togashi</a><div class="tooltip tooltip1"><p><i class="fa fa-user" aria-hidden="true"></i>&nbsp;&nbsp;&nbsp;Yota_Togashi</p><p><i class="fa fa-envelope" aria-hidden="true"></i>&nbsp;&nbsp;116***47@qq.com</p></div></span>4年前 (2018-12-16)</div></div></li><!-- #comment-## -->
<li class="comment odd alt thread-odd thread-alt depth-1" id="comment-38646"><span class="comt-f">#0</span><div class="comt-avatar wrapper"><i style="font-size:36px;" class="fa fa-user-circle" aria-hidden="true"></i><div class="tooltip"><p><i class="fa fa-user" aria-hidden="true"></i>&nbsp;&nbsp;&nbsp;爱睡觉的懒猫</p><p><i class="fa fa-envelope" aria-hidden="true"></i>&nbsp;&nbsp;wan***houyan@163.com</p></div><div id="runoobvote-id-38646" data-commid = "38646" class="upvotejs"><a class="upvote"></a> <span class="count">26</span></div></div><div class="comt-main" id="div-comment-38646"><p>Python 列表函数&方法的对象不仅可以是字符串也可以是列表。</p>

<pre>list1 = ["Googl",'Runoob',1997,2002]
list2 = [1,2,3,4,5,6]
list2.append(list1)print ("list2:",list2)</pre>
<p>输出结果如下：</p>

<pre>list2: [1, 2, 3, 4, 5, 6, ['Googl', 'Runoob', 1997, 2002]]</pre>

简单理解：python 在操作对象的时候，会根据自身对对象的定义进行操作，这里 list1 被定义的就是列表，那么 <a href="../python3/python3-att-list-append.html" target="_blank">list.append(obj)</a>
在操作 list1 时就作为列表追加。<div class="comt-meta wrapper"><span class="comt-author"><a target="_blank" href="javascript:;">爱睡觉的懒猫</a><div class="tooltip tooltip1"><p><i class="fa fa-user" aria-hidden="true"></i>&nbsp;&nbsp;&nbsp;爱睡觉的懒猫</p><p><i class="fa fa-envelope" aria-hidden="true"></i>&nbsp;&nbsp;wan***houyan@163.com</p></div></span>4年前 (2019-01-03)</div></div></li><!-- #comment-## -->
<li class="comment even thread-even depth-1" id="comment-51257"><span class="comt-f">#0</span><div class="comt-avatar wrapper"><i style="font-size:36px;" class="fa fa-user-circle" aria-hidden="true"></i><div class="tooltip"><p><i class="fa fa-user" aria-hidden="true"></i>&nbsp;&nbsp;&nbsp;冷瞳</p><p><i class="fa fa-envelope" aria-hidden="true"></i>&nbsp;&nbsp;126***3513@qq.com</p><p><i class="fa fa-external-link" aria-hidden="true"></i> <a rel="nofollow" target="_blank" href="https://www.cnblogs.com/neozheng/p/11219867.html">&nbsp;&nbsp;参考地址</a></p></div><div id="runoobvote-id-51257" data-commid = "51257" class="upvotejs"><a class="upvote"></a> <span class="count">52</span></div></div><div class="comt-main" id="div-comment-51257"><p><strong data-title>Python 中的 [:-1] 和 [::-1]</strong></p>

<p>1、案例解释</p>

<pre>a='python'
b=a[::-1]
print(b) #nohtyp
c=a[::-2]
print(c) #nhy
#从后往前数的话，最后一个位置为-1
d=a[:-1]  #从位置0到位置-1之前的数
print(d)  #pytho
e=a[:-2]  #从位置0到位置-2之前的数
print(e)  #pyth</pre>
<p>2、用法说明</p>

<pre>b = a[i:j]   # 表示复制a[i]到a[j-1]，以生成新的list对象

a = [0,1,2,3,4,5,6,7,8,9]
b = a[1:3]   # [1,2]

# 当i缺省时，默认为0，即 a[:3]相当于 a[0:3]
# 当j缺省时，默认为len(alist), 即a[1:]相当于a[1:10]
# 当i,j都缺省时，a[:]就相当于完整复制一份a

b = a[i:j:s]    # 表示：i,j与上面的一样，但s表示步进，缺省为1.
# 所以a[i:j:1]相当于a[i:j]

# 当s&lt;0时，i缺省时，默认为-1. j缺省时，默认为-len(a)-1
# 所以a[::-1]相当于 a[-1:-len(a)-1:-1]，也就是从最后一个元素到第一个元素复制一遍，即倒序。</pre><div class="comt-meta wrapper"><span class="comt-author"><a target="_blank" href="../note/51257">冷瞳</a><div class="tooltip tooltip1"><p><i class="fa fa-user" aria-hidden="true"></i>&nbsp;&nbsp;&nbsp;冷瞳</p><p><i class="fa fa-envelope" aria-hidden="true"></i>&nbsp;&nbsp;126***3513@qq.com</p><p><i class="fa fa-external-link" aria-hidden="true"></i> <a rel="nofollow" target="_blank" href="https://www.cnblogs.com/neozheng/p/11219867.html">&nbsp;&nbsp;参考地址</a></p></div></span>3年前 (2020-03-05)</div></div></li><!-- #comment-## -->
<li class="comment odd alt thread-odd thread-alt depth-1" id="comment-55993"><span class="comt-f">#0</span><div class="comt-avatar wrapper"><i style="font-size:36px;" class="fa fa-user-circle" aria-hidden="true"></i><div class="tooltip"><p><i class="fa fa-user" aria-hidden="true"></i>&nbsp;&nbsp;&nbsp;未来我来</p><p><i class="fa fa-envelope" aria-hidden="true"></i>&nbsp;&nbsp;951***665@qq.com</p></div><div id="runoobvote-id-55993" data-commid = "55993" class="upvotejs"><a class="upvote"></a> <span class="count">30</span></div></div><div class="comt-main" id="div-comment-55993"><p>列表遍历：</p>



<pre># 正序遍历：
list01 = ["Googl",'Runoob',1997,2002]
for i in range(len(list01)):  #用法1    
    print(list01[i])
for item in list01:  #用法2    
    print(item)
# 反向遍历

for i in range(len(list01) - 1, -1, -1):    
    print(list01[i])</pre><div class="comt-meta wrapper"><span class="comt-author"><a target="_blank" href="javascript:;">未来我来</a><div class="tooltip tooltip1"><p><i class="fa fa-user" aria-hidden="true"></i>&nbsp;&nbsp;&nbsp;未来我来</p><p><i class="fa fa-envelope" aria-hidden="true"></i>&nbsp;&nbsp;951***665@qq.com</p></div></span>3年前 (2020-08-06)</div></div></li><!-- #comment-## -->
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